This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-206889 filed on Jul. 6, 2001.
The present invention relates to a multilayer circuit board and a method for manufacturing the multilayer circuit board, especially relates to a multilayer circuit board that has electrodes, which are used for the connection with a chip component, only on one surface of the board and to a method for manufacturing the multilayer circuit board.
A conventionally known multilayer circuit board of the same type is manufactured using a plurality of so-called double-sided boards as follows. Each double-sided board includes a thermosetting resin film and a plurality of conductor layers, which are located on two surfaces of the thermosetting resin film. The conductor layers on one surface are electrically connected to the conductor layers on the other surface. The plurality of double-sided boards are piled with a plurality of interconnecting boards, which include unset thermosetting resin films in B stage and are ready for electrically connecting the conductor layers, such that the interconnecting boards are interleaved with the double-sided boards. At the same time, an unset thermosetting resin film is piled to cover one surface, to which the chip component is not connected, of the piled body, which includes the interconnecting boards and the double-sided boards. Then, the piled body, which includes the interconnecting boards, the double-sided boards, and the unset thermosetting resin film, is pressed and heated to complete the conventionally known multilayer circuit board.
Another conventionally known multilayer circuit board is manufactured as follows. An interconnecting board and a conductive foil are piled in this order on each surface of a double-sided board. After the piled body, which includes the double-sided board, the interconnecting boards, and the conductive foils, is pressed and heated, the conductive foils formed on both surfaces of the double-sided board are shaped by etching. An intermediate multilayer circuit board having the predetermined number of layers is formed by repeating a series of the piling, pressing, heating, and etching steps. After an unset thermosetting resin film is piled with the intermediate multilayer circuit board to cover one surface of the board, the piled body, which includes the intermediate multilayer circuit board and the unset thermosetting resin film, is pressed and heated to complete the another conventionally known multilayer circuit board.
In the methods for manufacturing conventionally known multilayer circuit boards described above, after a plurality of double-sided boards and a plurality of interconnecting boards are formed separately, the two are combined together, or after one double-sided board and a plurality of interconnecting boards are formed separately, they are combined with the conductive foils and. Therefore, the manufacturing process is relatively complicated.
The present invention has been made in view of the above aspects with an object to provide a multilayer circuit board, the manufacturing process of which can be simplified even if the multilayer circuit board has electrodes used for connection with a chip component only on one surface of the board, and to provide a method for manufacturing the multilayer circuit board.
A plurality of conductor layers are formed on a resin film made of thermoplastic resin to form a single-sided conductor layer film. Then, a plurality of via-holes, which are bottomed by the conductor layers, are formed in the single-sided conductor layer film. Then an interlayer connecting material is packed in the via-holes to form a single-sided conductor layer film having the interlayer connecting material. A plurality of single-sided conductor layer films are formed and stacked such that surfaces having the conductor layers face in the same direction. Then, the single-sided conductor layer films are pressed and heated to complete the multilayer circuit board, which has electrodes only on one surface. The multilayer circuit board is formed by using only the single-sided conductor layer films and pressing once, so the manufacturing process is simplified.